Smooth muscle is an integral part of hollow organs. Many of them are constantly subjected to mechanical forces that alter organ shape and modify the properties of smooth muscle. To understand the molecular mechanisms underlying smooth muscle function in its dynamic mechanical environment, a new paradigm has emerged that depicts evanescence of myosin filaments as a key mechanism for the muscle’s adaptation to external forces in order to maintain optimal contractility. Unlike the bipolar myosin filaments of striated muscle, the side-polar filaments of smooth muscle appear to be less stable, capable of changing their lengths through polymerization and depolymerization (i.e., evanescence). In this review, we summarize accumulated knowledge on the structure and mechanism of filament formation of myosin II and on the influence of ionic strength, pH, ATP, myosin regulatory light chain phosphorylation, and mechanical perturbation on myosin filament stability. We discuss the scenario of intracellular pools of monomeric and filamentous myosin, length distribution of myosin filaments, and the regulatory mechanisms of filament lability in contraction and relaxation of smooth muscle. Based on recent findings, we suggest that filament evanescence is one of the fundamental mechanisms underlying smooth muscle’s ability to adapt to the external environment and maintain optimal function. Finally, we briefly discuss how increased ROCK protein expression in asthma may lead to altered myosin filament stability, which may explain the lack of deep-inspiration–induced bronchodilation and bronchoprotection in asthma.
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1 March 2021
Review|
February 19 2021
Filament evanescence of myosin II and smooth muscle function
Lu Wang
,
Lu Wang
2
Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
3
The Centre for Heart Lung Innovation, University of British Columbia, Vancouver, British Columbia, Canada
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Pasquale Chitano
,
Pasquale Chitano
1
Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
3
The Centre for Heart Lung Innovation, University of British Columbia, Vancouver, British Columbia, Canada
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Chun Y. Seow
1
Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
3
The Centre for Heart Lung Innovation, University of British Columbia, Vancouver, British Columbia, Canada
Correspondence to Chun Y. Seow: chun.seow@hli.ubc.ca
Search for other works by this author on:
2
Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
3
The Centre for Heart Lung Innovation, University of British Columbia, Vancouver, British Columbia, Canada
Pasquale Chitano
1
Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
3
The Centre for Heart Lung Innovation, University of British Columbia, Vancouver, British Columbia, Canada
Chun Y. Seow
1
Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
3
The Centre for Heart Lung Innovation, University of British Columbia, Vancouver, British Columbia, Canada
Correspondence to Chun Y. Seow: chun.seow@hli.ubc.ca
This work is part of a special collection on myofilament function and disease.
Received:
September 30 2020
Accepted:
January 19 2021
Online Issn: 1540-7748
Print Issn: 0022-1295
Funding:
Canadian Institutes of Health Research
(PJT-153296)
Natural Sciences and Engineering Research Council of Canada
(RGPIN-2017-04976)
© 2021 Wang et al.
2021
This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms/). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 International license, as described at https://creativecommons.org/licenses/by-nc-sa/4.0/).
J Gen Physiol (2021) 153 (3): e202012781.
Article history
Received:
September 30 2020
Accepted:
January 19 2021
Citation
Lu Wang, Pasquale Chitano, Chun Y. Seow; Filament evanescence of myosin II and smooth muscle function. J Gen Physiol 1 March 2021; 153 (3): e202012781. doi: https://doi.org/10.1085/jgp.202012781
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